Face-type seals generally have a pair of relatively stiff primary or rotary seal rings and a pair of secondary seals or torics of elastic material. The seal rings have abutting mating faces of a hard, wear resistant metal. The torics are positioned between an adjacent seal housing and the back side of their associated seal ring. One seal housing is typically on a stationary member, for instance an axle housing, while the other seal housing is usually on a rotating member, for instance a wheel hub or the like. The elastic torics serve a dual function. Firstly, the torics provide a static seal between their associated seal ring and seal housing. Secondly, the torics provide an axial load on their respective seal rings to ensure fluid tight face-to-face contact between the primary seal rings.
U.S. Pat. No. 3,180,648, issued Apr. 27, 1965 to Kupfert et al and assigned to the assignee of this application shows a typical face-type seal.
The prior art seals perform well in applications, such as track roller or final drives of track-type vehicles, which operate at moderate speeds. In higher speed applications, such as in axles of off-highway trucks, and the like, the pressure-velocity limits of the hard materials used for the seal rings can be exceeded. This can result in the scoring of the contacting sealing faces of the seal rings which leads to leakage of the lubricant and the ultimate failure of the seal itself and the components which the seal is employed to protect.